The present invention generally relates to measuring the torque on a rotatable shaft and more particularly to non-intrusively measuring the torque on a shaft at high rotational speeds.
Historically, torque measuring for vehicles has been performed using a dynamometer in a laboratory setting. A dynamometer is used to determine the amount of horsepower an engine generates. A dynamometer includes an engine under test, a drive shaft and a torque measuring sensor. The engine is run under an artificial load, and the torque sensor measures the amount of torque the drive shaft is subjected to while the engine is operated at a constant speed. Since engine horsepower is equal to the torque times the rotational speed of the engine, if the engine is held to a constant rotational speed, the amount of torque can be measured and the amount of horsepower the engine generates can be obtained. Once the amount of horsepower is determined, adjustments to the control of the engine can be made to increase the amount of horsepower generated.
Conventional methods and apparatus for measuring torque in real time on a vehicle involve mounting large invasive devices on the drive shaft of the vehicle to determine the amount of torque generated by the engine. However, because these devices are invasive, they negatively effect the performance of a vehicle using the device by adding mass, increasing the tire path of the vehicle, and changing the center of gravity of the vehicle. As a result, with conventional technology the benefit of controlling engine performance using actual horsepower generated is outweighed by the additional weight and performance restrictions created by the conventional torque measuring devices.
In high performance automobiles in particular, adjustment of engine control in real time to produce the maximum amount of horsepower from the vehicle's engine is beneficial. However, the conventional sensors are limited to engine speeds less than 5,000 rotations per minute (RPM) because the sensing devices become separated from the driveshaft due to the extreme torque experienced at higher engine speeds. Since high performance automobiles operate at engine speeds of 5,000 RPM and higher, conventional sensing devices are not capable of providing real time sensing of torque. Additionally, as stated above, the conventional torque sensors are intrusive and negatively effect the performance of the engine due to their position on the driveshaft. This becomes amplified in high performance vehicles which are more susceptible to variations in weight and other performance modifications. As a result, a need exists to provide a torque sensor capable or withstanding engine speeds at high RPMs and that does not effect the performance of the vehicle.